Matek F405 mini TE IMU drift in pitch & roll

Hi everyone,

We have found some issue with these board in a 9in quadcopter.

After make a very good accels calibration, in the next boot, the pitch and roll angles, seen on the artificial horizon in Mission Planner appears very accurate.

Then, in a few seconds, starts to drift, increase angles a lot about 5-10 degrees. If i armed and fly, at the start of flight the drone works well, but, progressively goes drift in pitch and roll, and i have to compensate manually to make a hover.

anyone knowks the root of these drift imu values? is not safely to fly with these issue.

thanks.

pd: we have 0 periphericals powering by the board, all devices have power by external bec.